The field of the invention is dehydrogenation of aromatic carbon compounds and the present invention is particularly related to a method for the production of ethylbenzene by the dehydrogenation of cycloolefins having 8 carbon atoms in the presence of an aromatization catalyst.
Ethylbenzene is produced on a commercial scale by the alkylation of benzene with ethylene. Inasmuch as a constantly growing demand for aromatics is to be expected, one can also reckon with an increasing shortage of benzene.
The state of the art of ethylbenzene manufacture may be ascertained by reference to Kirk-Othmer "Encyclopedia of Chemical Technology", Vol. 19, 2nd Edition (1969), pp 57-62 and U.S. Pat. No. 3,903,185 the disclosures of which are incorporated herein. The state of the art of dehydrogenating non-aromatic cyclic compounds to aromatic compounds may be ascertained by reference to U.S. Pat. No. 2,745,887. The raw materials of the present invention are prepared as disclosed in U.S. Pat. Nos. 3,897,508 and 3,917,730, and the catalysts are prepared as disclosed in U.S. Pat. No. 2,836,633 and British Patent 1,259,535, the disclosures of which are incorporated herein.
Attempts have already been made to produce ethylbenzene by methods other than alkylation of benzene with ethylene.
U.S. Pat. No. 2,745,887 discloses a process for treating with alkali metals cyclic hydrocarbons having 6 carbon atoms in the ring and containing at least two double bonds, at least one of them in the ring. However, this process is useless for commercial purposes since induction periods of 12-15 hours occur before the reaction is initiated, unless activators are added such as, for example, o-chlorotoluene, which reduce the induction period to 4 - 5 hours, or unless the process is carried out in the presence of extremely expensive and dangerous sodium hydride. However, even in these cases, only degrees of conversion of up to 71 percent are attained. Furthermore, it was found that this process does not yield useful results when vinylcyclohexene is used.
Furthermore, it is known from U.S. Pat. No. 3,903,185 that cycloolefins having 8 carbon atoms can be conducted over catalysts of Subgroups VI to VIII, including the platinum group, of the Periodic TAble of the elements, at temperatures of 350.degree.-450.degree. C, under pressures of 2.5 - 30 atmospheres absolute and in the presence of 0.2 - 20 m.sup.3 of hydrogen per kilogram of C.sub.8 -cycloolefin, to obtain ethylbenzene in rather satisfactory yields. However, this process is commercially very expensive, because it must be carried out at high temperatures, under pressure, and in the presence of hydrogen.